PIR sensors are used to detect motion for example to turn on or off a light bulb when motion is detection. One such sensor is HC-SR501 motion detector, which costs around $1, and is tiny (32 x 24 mm), but not quite thin due to the design that needs to capture infrared light, with an height of around 2 centimeters. If you’d like something almost as cheap, just as small, but much thinner, microwave radar modules could be a good alternative.

XYC-WB-DC Microwave Radar Module vs HC-SR501 PIR Sensor

XYC-WB-DC is one of those modules with the following specs:

Operating Frequency – 5.8 GHz

Detection angle – 360°

Detection range – 6-9 meters

Working Voltage – 3.3-20VDC;

Standby current – <3mA;

Transmit power – <2mW;

Dimensions – 32 x 23 mm

Operating temperature range – -20 ~ +80 Centigrade;

Potential advantages over PIR sensors include wider detection angle, and lower power consumption, HC-SR501 datasheet reports respectively 120 degrees detection, and 65 mA “power consumption” @ 5V. The range is about the same for both PIR and Microwave radar modules, but the microwave module will also work through walls (which may be an advantage or an inconvenient), and the signal can be blocked by metal.

The module will output high signal (3.3V) when motion is detected, and the detection delay can be adjusted from 1 second to hundreds of second (two minutes max) by adjusting R6 resistor on the board as explained on this Taobao page (Chinese). By default there’s no resistor and the delay is 30 seconds, and you can adjust the delay by using 1K to 250K resistor.

I’m not sure what the other resistor (10K – 100K) is used for (maybe max distance), which brings me to the downside that there’s absolutely no info in English. However, I found this module on Pete Scargill blog, who tried it, and could confirm motion is properly detected.